2,275 research outputs found
Are the Perseus-Pisces chain and the Pavo-Indus wall connected?
A significant empty region was found between the southern Pavo- Indus (PI)
wall and the northern Perseus-Pisces (PP) chain. This survey tests the reality
of this void which may simply reflect previous poor sampling of the galaxies in
this region. Redshifts for a magnitude selected sample of 379 galaxies were
obtained covering the four UKST/SERC survey fields with Bt <= 17.0. All
redshifts were obtained with the FLAIR multi-object spectroscopy system on the
1.2 m U.K. Schmidt Telescope at Siding Spring, Australia. Two highly
significant density enhancements were found in the galaxy distribution at 133
Mpc and 200 Mpc (Ho=75 km/s/Mpc). We claim that no connexion exists between PP
and PI. However, a southern extension of PP was detected and makes the total
length of this chain of more than 150 Mpc.Comment: 14 pages, postscript including tables and figures
The Mid-Infrared Tully-Fisher Relation: Calibration of the SNIa Scale and Ho
This paper builds on a calibration of the SNIa absolute distance scale begun
with a core of distances based on the correlation between galaxy rotation rates
and optical Ic band photometry. This new work extends the calibration through
the use of mid-infrared photometry acquired at 3.6 microns with Spitzer Space
Telescope. The great virtue of the satellite observations is constancy of the
photometry at a level better than 1% across the sky. The new calibration is
based on 39 individual galaxies and 8 clusters that have been the sites of well
observed SNIa. The new 3.6 micron calibration is not yet as extensively based
as the Ic band calibration but is already sufficient to justify a preliminary
report. Distances based on the mid-infrared photometry are 2% greater in the
mean than reported at Ic band. This difference is only marginally significant.
The Ic band result is confirmed with only a small adjustment. Incorporating a
1% decrease in the LMC distance, the present study indicates Ho = 75.2 +/- 3.0
km/s/Mpc.Comment: Accepted for publication in The Astrophysical Journal Letters, 6
pages, 2 figure
Bimodality of Galaxy Disk Central Surface Brightness Distribution in the Spitzer 3.6 micron band
We report on measurements of the disk central surface brightnesses (mu0) at
3.6 microns for 438 galaxies selected by distance and absolute magnitude
cutoffs from the 2350+ galaxies in the Spitzer Survey of Stellar Structure in
Galaxies (S4G), one of the largest and deepest homogeneous mid-infrared
datasets of nearby galaxies. Our sample contains nearly 3 times more galaxies
than the most recent study of the mu0 distribution. We demonstrate that there
is a bimodality in the distribution of mu0. Between the low and high surface
brightness galaxy regimes there is a lack of intermediate surface brightness
galaxies.
Caveats invoked in the literature from small number statistics to the
knowledge of the environmental influences, and possible biases from low signal
to noise data or corrections for galaxy inclination are investigated. Analyses
show that the bimodal distribution of mu0 cannot be due to any of these biases
or statistical fluctuations. It is highly probable that galaxies settle in two
stable modes: a dark matter dominated mode where the dark matter dominates at
all radii - this gives birth to low surface brightness galaxies - and a
baryonic matter dominated mode where the baryons dominate the dark matter in
the central parts - this gives rise to the high surface brightness disks. The
lack of intermediate surface brightness objects suggests that galaxies avoid
(staying in) a mode where dark matter and baryons are co-dominant in the
central parts of galaxies.Comment: Accepted for publication in MNRAS, 9 pages, 10 figures, 1 tabl
BIOFUELS, AGRICULTURE AND CLIMATE CHANGE
In the context of ever-increasing petroleum prices combined with concerns about climate change, timing of adoption and rate of diffusion of land-based fuels and backstop technologies for transportation use are examined in this paper. A global model of land allocation joined with a Hotelling model has been developed. Using this framework, effects of climate and energy policies on world agricultural and energy markets have been explored. Further, their regional impacts are also analyzed. Whereas mandatory blending bio-fuels have substantial effects on world food prices and do not succeed in curbing down carbon emissions fluxes, carbon targets are expected to speed up date of adoption of backstop technologies. Then, sensitivity scenarios with regards to technological parameters reveal that higher is the rate of technological change, earlier backstop technologies are adopted and lower is the stock of carbon accumulated into the atmosphere. Finally, interplay between land-based fuels and deforestation has been studied. Results show that land-based fuels production speeds up world deforestation and causes substantial carbon emissions due to conversion of forests into agricultural lands.Ricardian rents, land use, biofuels, Resource /Energy Economics and Policy,
Alien Registration- Gregor, Helene G. (Portland, Cumberland County)
https://digitalmaine.com/alien_docs/23229/thumbnail.jp
Variation in the seston C:N ratio of the Arctic Ocean and pan-Arctic shelves
Studying more than 3600 observations of particulate organic carbon (POC) and particulate organic nitrogen (PON), we evaluate the applicability of the classic Redfield C:N ratio (6.6) and the recently proposed Sterner ratio (8.3) for the Arctic Ocean and pan-Arctic shelves. The confidence intervals for C:N ranged from 6.43 to 8.82, while the average C:N ratio for all observations was 7.4. In general, neither the Redfield or Sterner ratios were applicable, with the Redfield ratio being too low and the Sterner ratio too high. On a regional basis, all northern high latitude regions had a C:N ratio significantly higher than the Redfield ratio, except the Arctic Ocean (6.6), Chukchi (6.4) and East Siberian (6.5) Seas. The latter two regions were influenced by nutrient-rich Pacific waters, and had a high fraction of autotrophic (i.e. algal-derived) material. The C:N ratios of the Laptev (7.9) and Kara (7.5) Seas were high, and had larger contributions of terrigenous material. The highest C:N ratios were in the North Water (8.7) and Northeast Water (8.0) polynyas, and these regions were more similar to the Sterner ratio. The C:N ratio varied between regions, and was significantly different between the Atlantic (6.7) and Arctic (7.9) influenced regions of the Barents Sea, while the Atlantic dominated regions (Norwegian, Greenland and Atlantic Barents Seas) were similar (6.7â7). All observations combined, and most individual regions, showed a pattern of decreasing C:N ratios with increasing seston concentrations. This meta-analysis has important implications for ecosystem modelling, as it demonstrated the striking temporal and spatial variability in C:N ratios and challenges the common assumption of a constant C:N ratio. The non-constant stoichiometry was believed to be caused by variable contributions of autotrophs, heterotrophs and detritus to seston, and a significant decrease in C:N ratios with increasing Chlorophyll a concentrations supports this view. This study adds support to the use of a power function model, where the exponent is system-specific, but we suggest a general Arctic relationship, where POC = 7.4 PON0.89
Comparing The Impact Of An Astronomy Course And A Science And Society Seminar On Undergraduate Students' Attitudes Toward Science
A common challenge among university professors is how to best design undergraduate courses to successfully enhance students' attitudes. To compare which curriculum was more efficient at fostering a positive attitude towards science in general, I studied the impact of two different general education science courses on the attitudes of college students. The first course was an arithmetic-based Introductory Astronomy course for non-science majoring undergraduates that used interactive and inquiry-based teaching techniques. The comparison course was a Science, Technology, & Society (STS) seminar with context-based science contents, discussions, and intensive reading and writing. The post-semester results showed that neither curriculum on its own significantly changed the overall attitude of students towards science as far the assessment could measure, but that each curriculum did successfully enhance specific aspects of the studentsâ attitude in differing categories. The STS students had scores showing a gain in believing that scientists are honest. The astronomy students had scores showing a gain in understanding that scientific theories can change in the light of new evidence. However, the most significant change was a loss in the astronomy studentsâ confidence that the general public can and should understand science. Thus, the results suggest that professors who strongly desire to enhance the broad nature of students' attitudes need to use more purposeful instructional experiences rather than rely only on students' deepening understanding of the specific scientific content
Interpreting for Cross-Cultural Research: Changing Written English to American Sign Language
The quality of cross-cultural research depends on the skills of the investigators and interpreters who participate in each study. This paper addresses sign language interpreters\u27 participation in translating quantitative instruments from written English (source language) into American Sign Language (target language) for use in cross-cultural studies of people who are part of Deaf culture. First, research goals should be explicitly identified as either operational or comparative, and matched appropriately with an asymmetrical or symmetrical translation strategy. Next, interpreters often use a back translation process, with multiple checks on the conceptual integrity of the target language version of the instrument. Qualifications for a research interpreter are described in terms of language competencies and professional maturity. Data gathered through carefully translated instruments strengthens the validity of study findings, and avoids misrepresentation of the people from the culture under study
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